Magnesium is an obligatory co-factor in many enzymes in the human body.Magnesium may lower blood vessel tone, improve heart energy function, decrease platelet stickness, stabilize cell membranes and protect against heart damage from stress Magnesium reduces the total cholesterol, LDL-C, VLDL-C and elevates HDL-C. We demonstrated intracellular magnesium is correlated to blood clot formation and exercise duration. This project will explore the impact of magnesium on quality of life and blood vessel reactivity in stable coronary artery disease patients.